When it comes to seeing your products on your website, there are a few things you'll need to do:
Once you've completed these steps you'll be able to see the products you've imported from Printful.
To accept payments in your store, you'll need to enable one (or more) payment providers in Settings/Payment Providers - You can view a full list of payment providers available for your country by selecting your country from this list.
If you're based in a country where Shopify Payments is available, then you'll see Shopify Payments show up in Settings/Payment Providers automatically. All you'll need to do is complete the setup process by entering the requested information.
If you're in a country where Shopify Payments is not available, then you'll need to create an account with a third-party payment provider before enabling them in the Shopify admin.
Let me know if you have any questions.